The present invention relates to an orthopaedic prosthesis, and more particularly to a prosthesis with an access recess in the collar to facilitate loosening and subsequent removal of the stem from the bone.
It is known that orthopaedic prostheses may be secured into a bone with bone cement. There are times when it becomes necessary to remove a cemented prosthesis from the bone, and thus the prosthesis must be loosened from the cement. The cement generally forms a layer having a thickness between the bone and the prosthesis. It is well known in the art of orthopaedics to provide prostheses, such as femoral hip stem components, with collars or without collars. Collars typically extend outwardly from the stem in order to engage with or rest on the bone surrounding the cavity prepared for the stemmed implant. Some stems have no extending collar, while others have a circumferential collar extending from and surrounding all sides of the prosthesis, while others just have a collar extending on one or more selected sides, for example, extending just from the medial side. When it is determined necessary to remove a cemented stem from the bone, various tools, such as chisels or other suitable instruments, can be inserted between the prosthesis and bone into the cement to break up the cement and loosen the prosthesis from the cement. However, when a prosthesis includes an extending collar, it is difficult to break up the cement directly below the collar because it is not readily accessible.
It is also known to secure prosthetic implants without bone cement, such as by a press-fit or by biological ingrowth of bone into textured or porous surfaces or the like. If such prosthesis necessitates removal, the biological ingrowth bond to the implant must be broken to remove the implant. If there is an extending collar over portions of the stem affixed by biological ingrowth, it is difficult to break this bond directly below the collar because this portion is not readily accessible.
One way of dealing with this difficulty is described by U.S. Pat. No. 4,770,660 which provides a removable collar to enable access to the affixed surfaces of the implant beneath the collar. Another option is provided in U.S. Pat. Nos. 4,406,023 and 4,514,865 to Harris which discloses an implant which utilizes an enhanced fixation surface (either for biological fixation in '023 or cemented fixation in '865) only on the surfaces of the implant not directly beneath the extending collar.
Other devices are known for assisting with the removal of prostheses from a bone cavity. U.S. Pat. No. 4,919,153 to Chin discloses a ball clamp 32 connected to a slap hammer 22 for clamping about the head of a femoral component to pull the femoral component from the cement mantle. U.S. Pat. Nos. 4,612,922 and 4,399,813 to Barber disclose an apparatus for drilling into a prosthesis embedded in a bone shaft. The drilling apparatus of Barber has particular application to drilling into the end of a fragment of an elongated prosthesis which remains embedded in bone after fracture of the prosthesis.
Various tools and methods for removing the bone cement itself from the bone cavity are disclosed in the following U.S. Pat. Nos.: 5,019,083; 4,986,826; 4,873,969; 4,846,161; 4,702,236; 4,476,861.